Prior to the present invention, various methods are evaluated for treating rock to render the rock more resistant to environmental degradation. There have been many studies and methods of improving the quality of building stone and monuments, and limited study has been devoted to coarse aggregate quality improvement.
One study directed to aggregate improvement is shown by the interim report of May 1977, revised and updated January 1978, report PTI 7707 of the Pennsylvania Transportation Institute of Pennsylvania State University of P. V. Cady, "Upgrading of Poor or Marginal Aggregates for PCC and Bituminous Pavements". Various organic materials were evaluated as treating agents for improving the resistance of aggregate to degradation. Although valuable information has been generated from the aforementioned study, various solutions to the problem of aggregate degradation resulting from exposure to adverse environmental conditions including air pollution, moisture, or inorganic salt contact are constantly being evaluated. Improvement has been noted by using organic materials, such as epoxy resins, methyl methacrylate, etc., to treat marginal aggregate, but the degree of aggregate upgrading achieved has not warranted the cost of using such material unless the organics were extensively diluted in polluting organic solvents.
Standard engineering tests can be performed to predict the quality of aggregate. One procedure, for example, has been the magnesium or sodium sulfate soundness test, ASTM C88-76. In many instances, local high quality curse aggregate is not available for building construction and must be obtained at a high transportation cost. Various procedures have been used in an attempt to improve the quality of marginal or submarginal rock, for example, argillaceous limestone, highly crystalline limestone and graywacke sandstone to upgrade such material for use in portland cement, or bituminous or asphalt concrete. Procedures of the prior art have been found to be unacceptable because of economic or environmental reasons, or the treated rock failed to survive the magnesium or sodium sulfate soundness test.
Improved results have been achieved as shown by U.S. Pat. No. 4,256,501 of George M. Banino, based on the use of an organic solvent mixture of an organic condensation polymer and an aliphatic polyamine. However, organic solvent can present environmental pollution problems. In addition, the aforementioned aryl condensation polymer, for example, silicone-polycarbonate block polymers can significantly increase the cost of such treatment due to the expense of the starting reactants.
In my copending application Ser. No. 252,253, filed Apr. 9, 1981, there is taught that certain polyelectrolytes, that is polymeric substances in which the monomeric units of its constituent macromolecules possess ionizable groups, for example, polyethylenepolyamine, can be employed in the form of an aqueous solution to treat rock, stone or aggregate in the substantial absence of any unhardened cement, or material with adhesive and cohesive properties which make it capable of binding material fragments into a compact whole. It was found that the degradation of the treated rock was dramatically improved if the rock or aggregate was treated with the aqueous solution of polyelectrolyte and thereafter allowed to dry. The aggregate treated in accordance with Ser. No. 252,253 also was found to improve the compressive strength of portland cement compositions resulting from the cure of mixtures of portland cement concrete mixtures containing such treated aggregate. However, asphalt applied onto the surface of such aggregate treated in accordance with Ser. No. 252,253 was found to have a tendency to readily strip from the treated aggregate surface. For example, such asphalt coated aggregate failed the boiling water test used by the State of New York Department of Transportation to evaluate the soundness of coated materials employed in the construction of bridge decks and highways. The New York boiling water test is as follows:
Into a 200 cc container is placed 100 grams of aggregate as defined hereinafter. The container is then heated until the aggregate reaches a steady state temperature of about 150.degree. C. (300.degree. F.). There is then poured onto the heated aggregate 5-6 grams of AC10 or AC20 commercially available liquid asphalt preheated to a temperature of 150.degree. C. The resulting mixture is then stirred for 3-5 minutes and the blend is thereafter allowed to cool to room temperature.
About 175 ml of water is then poured into the container onto the asphalt coated aggregate until it is covered. The water is then heated to boiling. After 1 minute of a rolling boil, the aggregate is removed, drained and immediately doused with cold water. After the aggregate cools, it is drained and examined for bare spots. If the aggregate surface shows more than about 10% stripping, it is considered a failure. The percent stripping is based on a visual estimate of the approximate number of aggregate partially or completely free of asphalt, divided by the total number of asphalt coated aggregate initially used.
The present invention is based on the discovery that improved resistance to the stripping of asphalt can be achieved from the surface of aggregate treated with polyelectrolyte to improve its weatherability, in accordance with the method of Ser. No. 252,253 if a surfactant, as defined hereinafter, is utilized in combination with the polyelectrolyte initially used to treat the aggregate.